import java.util.LinkedList;
import java.util.Queue;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 蒋健
 * Date: 2022-01-24
 * Time: 9:15
 */
public class MyStack {
    private Queue<Integer> qu1;
    private Queue<Integer> qu2;

    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }

    public void push(int x) {
        if (!qu1.isEmpty()) {
            qu1.offer(x);
        } else if (!qu2.isEmpty()) {
            qu2.offer(x);
        } else {
            qu1.offer(x);
        }
    }

    public int pop() {
        if (empty()) {
            return -1;
        }
        if (!qu1.isEmpty()) {
            int size = qu1.size();
            for (int i = 0; i < size - 1; i++) {
                int val = qu1.poll();
                qu2.offer(val);
            }
            return qu1.poll();
        }
        if (!qu2.isEmpty()) {
            int size = qu2.size();
            for (int i = 0; i < size - 1; i++) {
                int val = qu2.poll();
                qu1.offer(val);
            }
            return qu2.poll();
        }
        return -1;
    }

    public int top() {
        if (empty()) {
            return -1;
        }
        if (!qu1.isEmpty()) {
            int val = -1;
            int size = qu1.size();
            for (int i = 0; i < size; i++) {
                val = qu1.poll();
                qu2.offer(val);
            }
            return val;
        }
        if (!qu2.isEmpty()) {
            int val = -1;
            int size = qu2.size();
            for (int i = 0; i < size; i++) {
                val = qu2.poll();
                qu1.offer(val);
            }
            return val;
        }
        return -1;
    }

    public boolean empty() {
        return qu1.isEmpty() && qu2.isEmpty();
    }
}
